Fuel consumption and flow rate

[Hanno Spoelstra]

Originally Posted by Phil Waterman

Wasn't there an electric fuel pump that was used in some of the Ford CMPs to help cure some fuel supply and vapor lock problems?

Yes, the Autopulse, it was standard on Indian Army CMPs. Read more here on its purpose and operation.

Hanno

[horsa]

I'd also done a lot of research into the use of electric fuel pumps on military vehicles during the war as a fix to operational problems in hot regions prior to going that route on my own T-16.

The modern pump I ended up using is rated for 4-7psi but this is restricted by the adjustable fuel pressure regulator that I have set at 3.5psi since the wartime manuals mention that pressure in association with the carburator.

Not sure how this equates to actual fuel flow since that would entail math formulas dealing with the pressure and capacity of the fuel lines

[Lynn Eades]

If I recall, the 94 and 97 stromberg carbs are delivered fuel at 2 1/2 to 3 1/2 psi. any more and the carb will flood. This pressure is achieved solely by the spring under the diaphragm in the mechanical pump.
If the carb is flooding from the electric pump when the engine is stopped, why wouldnt it be flooding, when its running (and vibribation is also happening)
There are three things here. delivery pressure, suction (the ability of the pump to lift the fuel to the pump measured in inches of mercury or the metric equivalent) and lastly the delivery volume.
It sounds to me, that you have too much pressure and not enough volume.
If you put a test gauge on your delivery pipe to the carb you can check the delivery pressure directly. If it is too high that will cause your carb to flood, and that can be a little tricky for even the mechanics among us to diagnose. (we can often wrongly decide its starving) Many of the electric pumps will deliver a hansome pressure. I saw one advertised recently at 8 1/2 psi. (Alfa Romeo used to have an adjustable pressure regulator called a "Fisba" for the carbs (Delorto, Webber, Solex)
My gut feeling is that you might have an air leak into the lines somewhere, between the pick up(s), and the pump suction side. these can be difficult to find. One of the prime possibilities will be the fuel change over valve (assuming you have one)
The best way to check this is run a temporary line (reservoir included) to the pump, and see how she goes.
If that fixes it, re introduce what ever sections you can, until you find the leak.
You could use a vacuum gauge on the suction side of the pump. Get a reading, and see if its the same at your fuel pick up pipes at the tank(s)
On the vapour lock, The original lines were steel not copper. This might help to slow the rate of heat transfer. Making up the pipes with the risk of vapour lock accuring in mind, might help.I have seen some really bad results.
Lastly, I would check that you have no blockages any where in the lines. I know a lot of it is new, but it is amazing where swarf, solder, thread tape, silicon, and every other type of gunge can get to, in a new system.
Hope this helps when your lost for ideas.

[cletrac (RIP)]

I've used electric pumps on daily driver vehicles and have found that you need to use a pressure regulator with a return line. If you use a dead head regulator then the pump will burn itself out in no time because it's putting out all the pressure it can all the time. With the return line the pump just makes whatever pressure you've got the regulator set at. A bonus with the return line is you totally eliminate vapour locking problems. Any vapour that forms is sent back to the tank in the return line. Also with the fuel circulating all the time you end up with cooler gas getting to the carb which helps with lots of problems. Any more I use a tank pump off a throttle body injection system since they last forever when just putting out 5 psi or so.

[andrew honychurch]

Wow, some great in put here thanks Guys. David, as you know I have pretty much copied your set up with the electric pump for all the reasons I highlighted above, and a pressure regulator with filter. Previous to getting the tanks resinstalled and making up new fuel pipes, I was running it on a Jerry Can with a small electric pump on the top. Made as a "get me home for the DUKW, if I got fuel pump/tank/line problems whilst at sea. I didnt fancy gradually sinking as I tried to get to grips with where the problem lay, sorry I digress. On the Jerry can the Carrier ran well with no overfueling problems but it did feel odd at higher revs. Almost as thoughyou had to keep accelerating to maintain steady engine revs. I did wonder whether the main jet was blocked and it was only working on the power jet and accelerator jet, but since it is a brand new Carb and really perfect, I dont think it is that. This led me to think that the electric pump on the Jerry can was perhaps not producing the flow necessary and therefore after accelerating there was a momentary loss of fuel requiring a few miliseconds to recharge.

Anyway, without getting to the bottom of that problem I have now fitting all new, copper, fuel line, new original specification "junior" fuel filter and as already mentioned the electric "facet" and fuel regulator. I too , have set this at 3.5 psi.

If the pump is left on for too long without starting the engine, it will overcome the carburettor float valve and flood. It may well be that the engine was designed to receive fuel at this pressure but of course the advantage of a mechanical pump is that it will not pump unless the engine is turning over, unlike the electric one.

I do worry that I may have too much head for the pump to manage to keep up with when the engine is running. In other words, yes it will flood when the engine is not turning over, but MAYBE as the pump and filterking are mounted high up it cannot keep up when engine is running? I have mounted the pump about the same height as the carburettor which is about 3 feet above the bottom of the fuel tank, which in turn is about six inches higher than the original fuel pump.

On the fuel return pipes, I fully get the advantage of returning unspent fuel to the tank, and have long been told that this will help remove the vapour locks back to the tank. However, since there is no obvious way to achive this without creating new pipes into the two fuel tanks ( or just one I suppose) I have left this alone. The Filter King advertises that it is able to negate the effects of vapourisation in its design.

http://www.demon-tweeks.co.uk/perfor...tor-and-filter

I am sure I am somewhere near achieving correct running but as Lynn says, it could be as simple as a vacuum leak somewhere or even a fault with the Governor. More digging is needed, and its stopped raining here in Kent, so I am off to play now. thanks chaps

[Lynn Eades]

Is your pump too high in relation to the tank?
Some pumps are good at pushing , but not lifting.
BTW Jerry cans are notorious for flaking paint on the inside.
Don't let it flood. It will bore wash the lube from the rings in your new motor.
just more thoughts.

[andrew honychurch]

Hi Lynn, the pump is about 0.2 metres above the bottom of the fuel tank, and looking at the Facet cylinder pump data, they will work at 0.3m so I think I am ok as far as that is concerned.

Anyway, I have just taken it out for a couple of miles across country. BLOOMIN FANTASTIC. she ran really well, and the electric pump and regulator seems, as David Gordon agreed, to have ironed out the idling and smooths out the performance. Not discernable flat spots and its getting better and better. Really pleased. The only bad news is its tracks have now got muddy!!

I am going to try to get one of my daughters to do a proper video in the next few days and I will get it posted up to YouTube. I think that the fuel problems may be solved thanks to me having a couple of lose fittings on the new pipes. As many are double flared fittings, they needed to bed down and then get another pinch on the pipe nuts. Fingers crossed. I defintely think it is not doing more than 3 or 4 mpg though! What a fun way to convert cash into hot gases though.

[Phil Waterman]

One more comment on electric pumps and ethanol I would add. I have had problems with electric pumps seizing or working poorly once they have had ethanol gas run through them and then have been allowed to stand open to the air dry.

Discovered this on test stand running in engines once used if the fuel pump was allowed to stand dry they failed. Had two of them do this in a row fortunately this happened both times with in a month of buying the pump and the auto parts store took them back. Now when I disconnect an pump from the engine or from the tank I make sure that the line and pump stay full of gas.

Just a thought.

Cheers Phil